@article{MS2_1990__66_1_167101,
     author = {Carlo Cecchini},
     title = {An abstract characterization of ...-conditional expectations.},
     journal = {Mathematica Scandinavica},
     pages = {155--160},
     publisher = {mathdoc},
     volume = {66},
     number = {1},
     year = {1990},
     zbl = {0748.46033},
     url = {http://geodesic.mathdoc.fr/item/MS2_1990__66_1_167101/}
}